The present invention relates to synchronous micrometers.
In certain known synchronous electric motors which utilize a magnet, a mechanical structure is provided to determine the direction of rotation of the motor so as to achieve a single direction of rotation instead of a two-directional rotation which otherwise would occur. However, such mechanisms have serious drawbacks and cause various difficulties. For example, it is known to use a shading coil in order to achieve a desired direction of rotation, but such structures are disadvantages in that they require an excessive consumption of power and as a result have an extremely low power efficiency. A two-phase electromotor utilizing a pair of electromotors of the two-directional type axially connected to each other has also the disadvantage of being very costly while occupying an undesirably large amount of space and having a low power efficiency.